Effects of Radial Loading Distribution on Partial-Surge-Initiated Instability in a Transonic Axial Flow Compressor

Partial surge is a new type of instability inception in the form of axisymmetric low-frequency disturbance located in the hub region and has been observed in transonic axial flow compressors. Previous studies on the evolution of instability in a transonic axial flow compressor at different rotor speeds found that partial surge occurs and leads to full compressor flow instability at high rotor speeds but not at low rotor speeds, and the blade loading at the hub increases with the rotor speed. A hypothesis is first made that the level of blade loading in the hub region could be highly correlated to the occurrence of partial surge. Experiments and numerical simulations are then conducted to test this hypothesis when the radial distribution of blade loading near the stall point is varied by introducing inlet distortion (i.e., alternately mounting specially designed screens at the inlet of the compressor). Both the experimental results of instability evolution and the numerical results of radial distribution of blade loading show that high hub loading near the stall point is the necessary condition for the occurrence of partial surge. In addition, the general effects of radial loading distribution on the type of stall inception are presented and discussed.